Separation of the constituents of gaseous mixtures



Nov. 16 ,1926.

' C. C. VAN NUYS SEPARATION OF THE CONSTITUENTS 0F GASEOUS MIXTURESFiled August 2, 1921 I W M 3 NE M MW [5 k wQ Hen. llll K 9 kw kw E Q w QPatented Nov. 16, 1926'.

our-r151 STATES PATENT OFFICE.

CLAUDE c. VAN NUYS, or CBANFOBD, NEw JEnsEmnssrGNo'n TO IR REDUCTIONcourm, INCORPORATED, A conroaa'rroN or NEw YORK.

' SEPARATION OF THE CONSIITUEN'IS OF GASEOU'S MIXTURES.

Applicationtled August 2, 1921. Serial No. 489,317.

This invention relates to theseparation from a gaseous mixture havingtwo or more components of one of these components, the criticaltemperatureof which is lower than 1 any temperature employed incarrying, out the method of partial liquefaction whereby the desiredresult is accomplished. While the method hereinafter described isparticularly adaptable for the separation of hydrogen from {water-gas orproducer-gas, it may be applied with like advantage to the separation ofa component-of any gaseous mixture, the constituents of which haveboiling points difi'ering from one another and which constituents may,with one exception, be liquefied under th conditions hereinafterdescribed.

It has been proposed heretofore to separate hydrogen gas by liquefactionmethods involving compressing and cooling. the mixture,- liquefying ascompletely as possible the condensible constituents therein by indirectcontact with preceding liquefied portions, evaporating at a lowerpressure, and expanding the uncondensible residue in an expansion engineor motor for the purpose of producing the refrigerative'eflect which isessential to the continuation of the method.

Such a method has the disadvanta e that the quantity of hydrogenavailable or expanslon with external work is generally in- 'suflicientto maintain the necessary refrigeration. It is, moreover, extremelydiflicult to design an expansion engine or motor to operatesatisfactorily upon hydro en as a working fluid. The tendency oft ehydrogen to leak around the piston and through the valves of the enginemakes the .operation of the expansion engine exceedingly'ineflicient andthe presence of small percentages of carbon monoxide in the un-.liquefiable hydrogenresidue makes such leakage dangerous to operators.In fact, 4 it has been foundgenerally necessary in the operation 'of themethod described, to recompress the separated hydrogen in an-auxlllarycompressor and to return it to the ex ansion engine for a secondexpansion inor er to maintain the necessary refrigerative efiectfthufsintroducing additional expense .iwith no compensating advantage. y

The operatlon'ofthis method has also the disadvantage than-t p eem fromwater-gas or producer-' through an economical and maintained in thecycle during the liquefaction of the incoming gaseous mixture isobtained in the low pressure hydrogen exhaust from the expansion engineand the liquefaction of the last portions of carbon monoxide or othercondensible gases are obtained by indirect contact with this gaseousengine exhaust. It is always diflicult to maintain constant the lowesttemperature in a liquefaction cold gas. In a metho employing a cold gasto maintain thelowest temperature of the cycle if, under variableoperating conditions, a change of temperature is produced in the gaseousrefrigerant, the effect is almost immediately to cause a variation ofthus a variation in the purit of the uncondensible efliuent. -It ispjref rable to stabilize the lowest temperature necessary to theoperation 'of th method by maintaining it evapoation of a body of coldliquid, since under such conditions the efi'ect of any variations ofrefrigerative effect is only to increase or' decrease the mass of coldliquid present, the evaporating temperature being necessarily fixed atany given pressure. With the method hereinbefore described, it isimpossible to attain this desirable object, and for this and otherreasons enumerated, the method cannot be efliciently operated andconsequently has found no broad application in the art.

, It is the object of the present invention .to overcome thedifiiculties referred to and to provide a method of efiicientlyseparating an uncondensible residue from a aseous mixture for the urposeof recovering the constituents forming the residue in a relativelypurecondition. a

,A further object of the invention 1s the provisionof a method of andapparatus for treating gaseous mixtures b to separate a desiredconstltuent thereof In commercially applicable manner. I

Further ob'ects and advantages of the invention will apparent as it isbetter understood by reference to the following specification andaccompanying Hrawing, am which an a paratus adapte to the accomlishmentoi the desired object is illustrated. o attempt has been made toillustrate tho details of the apparatus which persons 0 cle by means ofa iquefaction .the condensible constituents liquefied and skilled in theart may readily supply. Thus the drawing will serve to assist in thedisclosure of the invention without confusing it with the non-essentialfeatiires which form a part of every liquefaction system.

Let us assume for the purpose of clearly describing the method which isthe subject of the present invention that the mixture to be treated isordinary blue water-gas from which the moisture and carbon-dioxide hasbeen completely removed by suitable means 'so-that the mixture to betreated in the liquefaction cycle contains substantially 50% ofhydrogen, 1 to 3% of nitrogen and 47 to 49% of carbon monoxide.

A distinguishing feature of the present invention is the fact thatinstead of ex-- result of 'this'final selective panding theunliquefiable gaseous residue in an engine or motorin order to producethe necessary refrigeration to maintain a continous cycle, an auxiliaryexternal refrigeration cycle is employed with a working fluid which maybe either atmospheric air or a mixture containing substantially greaterproportions of nitrogen than, 15 present in atmospheric air.

According to the method herein disclosed, the major portion of therefrigerative effect required in the water-gas cycle is obtained bycirculating substantial quantities of pure nitrogen at atmosphericpressure and at a sufficiently low temperature -previously obtained byexpanding the nitrogen-with external work in a suitable engine orturbine in indirect contact and counter-current with the incomingwater-gas. The nitrogen thus employed is obtained from the separation ofthe oxygen-nitrogen mixture which constitutes the working fluid of theauxiliary refrigeration cycle hereinbefore mentioned. The maintenance ofthe constancy of the lowest temperature employed in the watergas cycleis not accomplished by means of this cold nitrogen exhaust. For thatpurpose, pure liquid nitrogen is employed at a pressure of oneatmosphere, or, if desirable, at a reduced pressure, this liquidnitrogen also being obtained in the manner hereinafter described fromthe auxiliary nitrogen-oxygen cycle.

The incoming water-gas mixture, after the major portion of the carbonmonoxide has been liquefied and thus separated by indirect contact withpreceding portions of liquid carbon monoxide at a pressure ofsubstantially one atmosphere, comes into indirect contact with the coldliquid nitrogen and the last portions of carbon monoxide and thenitrogen remaining in the mixture are thereby removed by liquefaction inthe tubes of a selective condenser employing backward return. Theliquefaction of is to produce an unthe principle of the gaseous mixtureoondensible vapor residue consisting substantially of hydrogen andcontaining not more than 1 to 2% of carbon monoxide and a small fractionof a percent of nitrogen. The uncondensible residue and also the carbonmonoxide-nitrogen obtained from the vaporization of the liquid producedin the water-gas condenser are brought into indirect contact by means ofsuitable heat interchangers with the incoming water-gas to assist in therefrigeration thereof as hereinafter descr'bed. The pure nitrogenemployed as above described to assist the separated water-gas products,in cooling the incoming water-gas together with the evaporated liquidnitrogen employed to produce the final condensation of the water-gascycle and also the remainder of the separated nitrogen employed in theauxiliary cycle, all at a pressure of substantially one atmosphere, areultimately returned to the main compressor of the auxiliary cycle whilethe oxygen mixture separated as hereinafter described in that cycle isrejected. Thus, ultimately the result is to attain a working fluid forthe auxiliary cycle composed of substantially greater percentages ofnitrogen than is contained in atmospheric air.

For reasons hereinafter pointed out, the upper limit of this nitrogencontent which can possibly be attained is around 93%. Accordingly, it ispossi le to obtain without rectification a working fluid in theauxiliary cycle, the major portion of which circulates in a closed cycleand from which it is unnecessary to initially remove moisture or carbondioxide. To this cycled nitrogen sufficient atmospheric air is added tocompensate for the oxygen mixture rejected as hereinafter described.

In the auxiliary cycle, the gaseous mixture after compression in themain auxiliary compressor is cooled in a suitable aftercooler and thenenters changers where it is further cooled by indirect contact with theseparated products obtained in that cycle and enters the bottom of aselective tubular condenser consisting of a plurality of vertical tubesand provided at the bottom with several rectification trays of the usualform to assist in obtaining the maximum possible degree of oxygenenrichment in the liquid deivered from the condenser. This maximumpossible enrichment is obtained when the liquid condensed at the bottomhas a composition necessary for phase equilibrium with the vapor mixtureentering the condenser. The uncondensed gaseous residue leaving the topof the auxiliary condenser and consisting substantially of pure nitrogenat the original pressure of the auxiliary compressor, is divided intotwo parts, the greater of v which is expanded with external work in asuitable engine or turbine in order to reduce its temperature to a pointpermitting its employment to the auxiliary inter-v .the other assists inthe ing valve and assist in refrigerating both the water-gas andauxiliary cycles. The second portion of the un'condensed residue leavingthe top of the auxiliary condenser is conducted to the bottom of theWater-gas condenser where it enters a plurality of closed tubes aroundwhich the liquid carbon monoxide which is condensed in the water-gascondenser collects. In vaporizing this liquid carbon monoxide, thenitrogen is liquefied and thereafter the liquid is conducted to the topsection of the water-gas condenser where it serves to liquefy the lastportions of carbon monoxide and nitrogen in the watergas. The exhaustleaving the nitrogen exgansion engine is divided into two portions;

ne portion is employed to refrigerate the water-gas cycle as alreadydescribed, and refrigeration of the auxiliary cycle.

The oxygen-enriched liquid produced at the bottom of the auxiliarycondenser is led through a pipe carrying a pressure reducis delivered tothe bottom portion of the space surrounding the tubes of the auxiliarycondenser where it is vaporized by condensing the gaseous mixtureascending in these tubes. The vapor thus formed is conducted througlntheauxiliary interchangers in indirect contact with the incoming fluidtherein. The temperature of the product of the oxygen-containin liquidis thus restored to substantially that of the atmosphere, and it is thenexpanded with external work in a suitable engine or motor in order tolower its temperature to a point permitting its employment to assist inthe refrigeration of the warm end of the auxiliary cycle. After such usein .which the temperature of the gas is restored to that of theatmosphere, it is rejected. This oxygen-containing product is the onlymixture leaving the auxiliary cycle, and it is apparent that itscomposition must ultimately become identical with that of the air whichenters the cycle. Similarly, the composition of the liquid roduced atthe bottom of the auxiliary con enser must also attain the samecomposition. This liquid will have a composition such that it is inphase equilibrium with the incoming vapor mixture circulating intheauxiliary cycle and it follows that the composition of the auxiliaryworking fluid which is compressed in the auxiliary compressor will bethat of a vapor having phase equilibrium with liquid air, i. e.,substantially 7% oxygen and 93% nitrogen.

In describing the apparatus illustrated in the drawing, attention will,first be given to the air or refrigerating cycle which is employed forthe urpose of insuring the necessary refrigeration for the water-gascycle. Referring to the drawing, 5 indicates a colcomprising a casing.divided by partiof the gaseous mixture in the tubes.

tions 6, 7, 8 and 9 into a plurality of compartments 10, 11, 12 and 13,the several functions of whirh will hereinafter appear. The coldcompressed gaseous mixture, which, in starting the apparatus, ispreferably air is delivered to the chamber 10 through a pipe 14 andpasses in the chamber through 'a plurality of rectification trays 15 ofthe usual type which support layers of liquid resulting from theselective liquefaction of the incoming gaseous mixture. serve topartially rectify this liquid, reducing the proportion of the morevolatile constituent therein and the liquid thus partially rectified isaccumulated in the bottom of the chamber 10.

The accumulated liquid is delivered through a pipe 16 and a pressurereducing valve 17 to the chamber 11 where it surrounds a plurality oftubes 18 extending through the partitions 6, 7 and 8 and communicatingwith the chamber 10. Thus the gaseous mixture entering the chamber 10 issubjected to indirect contact with a surrounding liquid, which, being ata lower pressure, serves to cool and liquefy portilt ililis e liquidthus formed flows downwardly in the tubesin direct contact with theincoming gaseous mixture and is enriched in the less volatileconstituent under the backward return principle. The liquid flowing downthe tubes is that which accumulates in the bottom -'of the chamber 10and is subsequently delivered to the chamber 11 where it in turn servesas a refrigerating medium.

Continuing through the tubes 18, the

gaseous mixture is subjected in the chamber 12 to indirect contact witha cold gaseous medium supplied as hereinafter described to the chamber.The residual gas which leaves the tubes at their upper ends escapesthrough a pipe 19. A portion of this gas ma r however )ass 11 ward]through a rec- .i i 7 l y tification tray 20 which supports a layer ofliquid and thence into closed tubes 21 extending into the chamber 13 andsurrounded therein by a medium which is supplied to the chamber 12. Thetubes 21 serve to produce a liquid which is delivered onto the tray 20and thence onto the partition 8 where it surrounds the upper ends of thetubes 18. It will be noted that the ends of the tubes 18 extend slightlyabove the partition in order to permit the accumulation 'of a layer ofliquid, and the surplus liquid overflows into the pipe 19, and isfinally delivered to the water gas column as hereinafter described. Thisarrangement insures suflicient'. liquid for the final treatment of thewater gas mixture under certain conditions which may prevent theformation of the required amount of liquid in the watergas column.

The vapor produced in the chamber 11 The trays portion of the coldgaseous through a end of the section A of the exchanger.

by the transfer of cold to the gaseous mixture in the tubes 18 isdelivered from the chamber through a pipe 22. Since this gas is verycold, it is employed directly in reducing the. temperature of theincoming gaseous mixture before it enters the column 5. For this purposea portion of the gas escaping through the pipe 19 is also utilized,being withdrawn through a pipe 23. An exchanger is employed for thepurpose of effecting the transfer of heat from the incoming mixture tothe outgoing gases. This exchanger preferably comprises sections A andB, each consisting of a casing enclosing a plurality of tubes 24 and 25about which the incoming gaseous mixture is caused to circulate bybafiles arranged in each section. Thus the gaseous mixture enteringthrough a pipe 31 is compressed in a compressor 32 cooled in anaftercooler 33 which may be supplied with cooling Water, for example,and is delivered through a pipe 34 to the sectlon' A of the exchanger.After traveling therethrough in the manner indicated by the arrows, thepartially cooled gas is delivered from the section A through a pipe35-to the section B of the exchanger, and similarly travelingtherethrough is delivered by the pipe 14 to the chamber 10 in the column5. A purge 36 controlled by a valve 37 permits the withdrawal ofmoisture accumulating in the section A of the exchanger.

The gas escaping from the chamber 11 through the pipe 22 is deliveredthereby to a chamber 38 at one end of the section B of theexchanger andtravels through the tubes 24 to a chamber 39 at the opposite end of thesection B. Thence it is delivered pipe 40 to a chamber 41 at the Aftertraveling through the tubes 24, it arrives at a chamber 42 at the end ofthe section A of the exchanger. When a sufiicient volume of the gas isobtained at a suitable pressure, as will occur under certain conditionsof operation, the gas is withdrawn from the chamber 42 through apipe 43controlled by a valve 44 and is delivered to an expansion engine orturbine 45 where it is.

expanded with external work and thereby cooled. The cold gas atsubstantially'atmospheric pressure is delivered through a pipe 46-to achamber 47 at the end of the section A of the exchanger and thencetravels through tubes 25 to a chamber 48 at the opposite end of thesection A of the exchanger. The gas is thence discharged through a pipe49 controlled by a valve 49 having given up its cold to the incomingmixture, and being, therefore, of no further utility in the operation.When the composition of the gas is approximately thatof air, it may bereturned with advantage to the cycle to replace the make-up air which isotherwise introduced. This obviates the necessity of scrubbing the airentering the cycle; A suitable connection 50 controlled by a valve 51'is provided for this purpose.

That portionof the gaseous effluent from the column 5 which is withdrawnthrough the pipe 23 is delivered thereby to a chamber 50 at one end ofthe section B of the exchanger and travels thence through tubes 25 to achamber 51 at the opposite end of the section B of the exchanger. Thegas thus warmed by indirect contact with the incoming gaseous mixture isdelivered by a pipe 52 controlled by a valve 53 to an expansion engineor turbine 54, where it is expanded with external work and therebycooled. The cold gas is delivered through a pipe 55 and a branch 56thereof controlled by a valve 57 to the chambers 12 and 13 of the column5, and is caused to circulate therein about the tubes 18 and 21 bybaflies 58 and 59 arranged within the cham-- bers. The gas escapesthrough a pipe 60 and a pipe 61 controlled bya valve 62, and a portionthereof is delivered by a pipe 63 communicating therewith to a 64 at theend of the section B of the exchanger. Thus the gas travels throughtubes 25 to a chamber 65 at the opposite end of the section B of theexchanger. A pipe 66 connects the chamber 65 with a chamber 67 at oneend of the section A of the exchanger and the gas travels thence throughtubes 25 to a chamber 68 at the opposite end of the section A, and isdelivered through a pipe 69 to a pipe 70 whereby it is returned to theinlet of the compressor 32. Thus this gas whichcon stitutes the workingfluid of the air column is returned to the cycle and may be employedrepeatedly without further purification for 133116 removal'of moistureand carbon diox- 1 e, fication. As already pointed out this gas willeventually approximate a composition having 93% "nitrogen and 7%'oxygen.

A portion of the gas escaping from the column 5 through the pipe 19 isdelivered by a pipe 91 to the'lower portion of the watergas column 92-,which comprises a shell divided by partitions 93, 94, 95 and 96 into aplurality of chambers 97, 98, 99 and 100. The gas entering the chamber97 from pipe 91 passes upwardly in closed tubes 101 which are surroundedby a body of liquid accumulating as a result of the selectiveliquefaction of the gaseous mixture therein. In the specific applicationof the method under con-.

sideration, the gas entering the tubes 10] is substantially purenitrogen, and the liquid surrounding the tubes is carbon-monoxide andnitrogen derived from the water-gas chamber thereby saving the expenseof this puri-' which is under treatment. The nitrogen liquefied in thetubes 101 accumulates in the bottom of the chamber 97 and is deliveredtherefrom together with liquid nitrogen supplied from the (olumn 5through a pipe 102 having a pressure reducing valve 103 to the chamber100 at the top of the column 92.

The water-gas after compression and cooling as hereinafter described, isdelivered through a pipe 104 to the chamber. 98 above the gas in tubestheliquidfsurrounding the tubes 101. It passes upwardly through trays105 of the usual form, carrying layers of liquid which arev produced bythe selective liquefaction of 106, extending through the partitions 94,95 and 96. In the tubes 106, the gas is subjected first to indirectcontact with liquid" accumulating in the chamber 98 and delivered to thechamber 99. through a pipe 0-3107 having a pressure reducing valve 1.08.

Thus, the liquid in the'chamber 99 is main tamed at a pressure somewhatlower than the pressure of the gaseous mixture entering the chamber 98,with the result that heat is transferred thereto from the gaseousmixture in the tubes. The liquid formed in the tubes flows downwardlytherein with enrichment in the less volatile constituent under theprinciple of backward return, and this liquid which accumulates in thechamber 98 is in turn delivered to the chamber 99. Continuing throughthe tubes mixture is subjected to the low temperature of the body ofliquid which is delivered to the chamber 100 through the pipe 102, and

substantially all of the constituents of the gaseous mixturewith theexception of the hydrogen are liquefied in the tubes 106 and returnedtherethroug h to the chamber 98, While the residual gas escapes througha pipe 109 from the column.

The vapor produced in the chamber 92 by the liquefaction of the gaseousmixture in the tubes 106-escapes through a pipe 110 and the vaporsimilarly produced in the chamber 100 escapes through a pipe 111. Thisgas, being substantially nitrogen which .is the working fluid of the aircycle, may be delivered through a pipe 112 controlled by a valve 113 tothe pipe 63, and thence returned to the compressor 32. Under-someconditions, it may be desirable to maintain a reduced pressnre in' thechamber 100, and consequently apipe 114 controlledby a valve 115communicates with the pipe 111 and with a vacuum pump 116. From thevacuum pump the gas is delivered through a pipe 117 controlled by avalve 118 to the thence returned to the compressor 32, giving 0 up itscold to the incoming gaseous mixture 106, the gaseousthe exchanger.

pipe 63 and is.

to transfer the exchanger consisting of sections 0 and D, is thereforeemployed and the water-gas entering through a pipe 119 is compressed bya compressor 120, cooled in an aftercooler 121 which may be suppliedwith cooling Water, and delivered through a pipe 122 to the section I)of the exchanger. The exchanger is provided with tubes 123 and 124, andbattles 125 causing the water-gas to circulate about the tubes. A pipe126 connects the sections C and D of the exchanger so that the astraveling therethrough is finall deliverec to the pipe 104 previouslyreferre to. A purge 127. provided with a valve 128 permits theWithdrawal of liquids condensed in the section D of the exchanger.

The gas escaping from the column 92 through the pipe 110 is deliveredthereby to a chamber 129 at one end of the section 0 of the exchangerand travels through tubes 124 to a chamber 130 at the opposite end ofthe exchanger. A pipe 131 connects the chamber 130 with a chamber 132 atthe end of the section D of the exchanger, and thence the gas travelsthrough tubes 124 to a chamber 133 at the opposite end of the section Dfrom which the gas escapes through a pipe 134. The gas may be deliveredthereby to a suitable storage receptacle, and used, for example, insuperheating the steam WhICh is utilized in the production of water gas.

The gas, forexample hydrogen, escaping from the column 92 through thepipe 109 is delivered thereby to a chamber 135 at the end of the sectionC of the exchanger and travels through tubes 124 to a chamber 136 at theopposite end of the section C of the exchanger A pipe 137 connects thechamber 136 to a. chamber 138 at the end of the section D of theexchanger and the gas travelsthence through tubes 124 to a chamber 139at the opposite'end of the section D of the exchanger. A pipe 140delivers the gas from. the chamber 139 to a suitable storage receptacle.

In the event that sufiicient refrigeration is not maintained by theoperation of the column 92 as hereinbefore described, a portion of thecold nitrogen from the pipe 63 may be withdrawn through a plpe 141 anddelivered to a chamber 142 at one end' of the section C of theexchanger. Trayelmg thence through tubes 123, the gas is delivered to achamber A pipe 144, controlled by a valve 145 connects the chamber 143to a chamber 146 at one end of the sectionD of the exchanger, and thegas travels thence through tubes 123 to a chamber 147 at the 149 and isdelivered to the pipeth70 and' e comthereby returned to the-inlet opressor 32. I

considerable pressure and in order Under certain conditions, hydrogenescap-' ing through the pipe 140 may be still at to utilize thispressure advantageously, a byass 150 controlled by a valve 151 is adapteto deliver the cooling nitrogen from the pipe 144 directly to the pipe148. The valves 145 and 149 being closed, the hydrogen may be withdrawnfrom the pipe 140 and delivered through a pipe 152 controlled by a valve153 to an engine or motor 154 where it is expanded with external workand thereby cooled. The cold hydrogen is delivered from a pipe 155 tothe chamber 146 at the end of the section D of the exchan er and travelsthrough tubes 123 to the c amber 147, from which it is withdrawn througha pipe 156 and delivered to a suitable storage receptacle.

From the foregoing description, it will be observed that, as pointed outheretofore, the gaseous mixture to be separated is finally subjected toa liquid cooling medium, designed to prevent variations in temperaturewhich affect the operation of refrigerating systems employing a gaseouscooling agent for the final cooling of the mixture. The liquid coolingagent is produced in an economical manner avoiding all losses whichmight result from the extensive rectification and recovering andutilizing the refrigerating effect to the fullest extent. It is possiblein producing the refrigerating liquid to recover a considerableproportion .of the energy originally expen ed in compressing thecirculating medium, and provision is made for such recovery in theengines or motors hereinbefore described. Since the working fluid of theair cycle circulates continuously, it need not be purified for theremoval of moisture or carbon dioxide except as additions of air to thecycle are required from time to time, and furthermore, since the workingfluid finally approaches a definite composition and consists primarilyof nitrogen, the losses due to energy expended in separating theconstituents are almost entirely obviated.

In the separation of Water-gas and similar gaseous mixtures in themanner hereinbefore described, a corresponding efliciency isaccomplished through the elimination of rectification, the separationbeing almost entirely accom lished by selective liquefaction with bacward return of the liquid constituents. A large proportion of the energyoriginally employed in compressing the gaseous m1 ture 1s recovered,particularly if the hydrogen is expanded in the manner hereinbeforedescribed. It is possible, therefore, to produce hydrogen, for example,from gaseous mixtures containing it, such as water gas, in an economicalmanner; and since water gas is available at relai tively slight expense,hydrogen ma be produced at a correspondingly low cost and in asatisfactory condition with respect to purity for numerous uses to whichit is adapted.

The inventlon herein described is particu-- larly adapted to employmentin the recovery of hydrogen from water gas, but it is equallyadvantageous'in separatin helium, for example, from natural gas, an infact, for the separation of any constituent of a gaseous mixture whichis. not readily liquefiable under conditions which ensure theliquefaction of other constituents. The claims are not, therefore,limited to the treatment of water gas, it being the intention to embraceall uses'to which the invention may be applied. 7

Various changes may be made in the details of operation and in theapparatus here inbefore described without departing from the inventionor sacrificing any of the advantages thereof.

I claim:

1.- A method of separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising subjecting the mixtureto. selective backward return condensation with previously liquefiedportions thereof evaporating at a lower pressure, and thereafter with anextraneous liquid eva crating at a lower temperature to selective yliquefy substantially all but the desired constituent of the mixture.

2. A method of separating a constituent which is not readilyliquefiablefrom a gaseous mixture, comprising subjecting the mixture toindirect contact with previously liquefied portions thereof evaporatingat .a lower pressure, then to indirect contact with an extraneousliquidevaporating at a lower pressure, and returning the selectivelyformed liquid in direct contact with the mixture undergoingliquefaction.

3. A method of separating a constituent which is not readily liquefiablefrom a gaseous mixture, comprising subjecting the mixture to selectivebackward return condensation with successively colder media, the finalmediumbeing an extraneous evaporating liquid.

4. A method of separating a constituent which is not readily liquefiablefrom a gaseous mixture, comprlsin subjecting the mixture to selectivelique action by indirect contact with successively colder media, thefinal medium being an extraneous evaporating liquid, and returning theselectively formed liquid in direct contact with the mixture undergoingliquefaction.

5. A method of separating a constituent which is not readily liquefiablefrom a gaseous mixture, comprising subjecting the mixture to selectiveliquefaction in successive stages, first by indirect contact withliquefied portions of the mixture, and then Eli eous mixture, comprisingsubjecting by indirect contact with a colder liquid, and employing theliquid resulting from the selective liquefaction to produce the colderliquid by indirect contact of an extraneous gaseous medium therewith.

6. A method of separating a constituent which is not readily liquefiablefrom a gaseous mixture, comprising subjecting the mixture to selectivebackward return condensation in successive stages, first by indirectcontact with liquefied portions of the mixture, and then by indirectcontact with a colder liquid evaporating at a pressure belowatmospheric.

7. A method of separating a constituent which is not readily liquefiablefrom a galsmixture to selective liquefaction by indirect contact withsuccessively colder media, the final medium being an extraneous liquidproduced by indirect contact of a gaseous medium with liquefied portionsof the mixture.

8. A method of separating a constituent whichis not readily liquefiablefrom a gaseous mixture, comprising, subjecting the mixture to selectiveliquefaction by indirect contact with successively colder media, thefinal medium being an extraneous 'liquid produced byindirect contact ofa cold gaseous medium with liquefied portions of the mixture, andsupplying cold to make up for heat leakage in-the system by heatinterchange of the mixture with other portions of the cold gaseousmedium.

9. A method of separating a constituent which is not readily liquefiablefrom a gaseous mixture, comprising subjecting the mixture to selectiveliquefaction by indirect contact with successively colder media, thefinal medium being an extraneous liquid produced by indirect contact ofa cold gaseous medium with liquefied portions of the mixture, andmaintaining a separate lique faction cycle to produce the cold gaseousmedium.

10. A method of separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising subjecting the mixture toselective backward return condensation with successively colder media,the final medium being an extraneous liquid produced from a maintaininga separate liquefaction cycle to supply the cold gaseous mediuml 11. Amethod of separating-a constituent which is not readily liquefiable froma gaseous mixture, comprising subjecting the mixture to selectivebackward return condensation with successively colder media, the finalmedium being an extraneous liquid, maintaining a separate liquefactioncycle to supply the extraneous liquid, and returning the vapor from thisliquid to the separate liquefaction cycle.

cold gaseous medium, and- 12. A method of separating a constituent whichis not readily liquefiable from a gaseous mixture, comprising subjectingthe mixture to selective liquefaction by indirect contact withsuccessively colder media, the final medium being a" liquid producedfrom an extraneous gaseous medium, maintaining a separate liquefactioncycle to supply the gaseous medium, and supplying the necessaryrefrigeration for the separate liquefaction cycle by expansion of theproducts thereof with externalwork.

13. A method of separating'a constituent which is not readilyliquefiable from a gaseous mixture, comprising subjectin the mixture toselective liquefaction by indirect contact with successively coldermedia, the final medium being an extraneous liquid produced by indirectcontact of a cold gaseous medium with liquefied portions of the mixture,withdrawing the vapor from the extraneous liquid, and returning it asthe gaseous medium to produce additional quantities of the extraneousliquid.

14. A method of separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising subjecting the mixture toselective liquefaction by indirect contact with successively coldermedia, the final medium being an extraneous liquid produced by indirectcontact of a cold gaseous medium with liquefied. portions of themixture,withdrawing the vapor from the extraneous liquid, recompressing thevapor, and returning it as the gaseous medium to produce additionalquantities of the extraneous liquid.

15. A method of separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising subjecting the mixture toselective liquefaction by indirect con tact with successively coldermedia, the final medium being an extraneous liquid, expanding theunliquefiable residue of the gaseous mixture, and utilizing the coldthereof to refrigerate the incoming gaseous mixture.

16. A method of separating a constituent which is-notlreadilyliquefiable from a gaseous mixture, comprising 'subjectin the mixture toselective liquefaction by indirect contact with successively coldermedia, the final medium being an extraneous liquid, mai'n' t'aining aseparate liquefaction cycle to supply gas for producing the extraneousliquid, and utilizing a portion of the gas as a refrigerating agent forthe incoming gaseous mixture. I

17. A method of separating a constituent which is not readilyliquefiable from 'a gaseous mixture, comprising subjecting the mix;

ture to selective liquefaction by indirectcontact with successivelycolder media, the final I medium being an extraneous liquid produced ofa gaseous medium with by indirect contact of the mixture,maintainliquefied portions.

ing a separate liquefaction cycle to provide the gaseous medium, andutilizing a portion of the gaseous medium to refrigerate the incominggaseous mixture.

18. A method of separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising subjecting the mixture toselective backward return condensation with successively colder media,the final medium being an extraneous liquid, maintaining a separateliquefaction cycle to supply gas for the extraneous liquid, andreturning the vapor from the extraneous liquid and substantially all ofthe product of the separate liquefaction cycle for recirculation in thecycle.

19. An apparatus for separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising a column having aplurality of chambers disposed one above the other each liquid, meansextending continuously through the chambers and adapted to convey thegaseous mixture in indirect contact with the liquids therein, means forsupplying liquid produced by selective liquefaction of the gaseousmixture to one of the chambers, and means for supplying an extraneousliquid to another of the chambers.

20. An apparatus for separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising a column having aplurality of chambers each adapted to receive a liquid, means extendingthrough the chambers and adapted to convey the gaseous mixture inindirect contact with the liquids therein, means produced by selectiveliquefaction of the gaseous mixture to one of the chambers, and meansfor supplying an extraneous liquid to another of the chambers, includingmeans for liquefying a gaseous medium by indirect contact with theliquid produced by selective liquefaction of the gaseous mixture.

21. An apparatus for separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising a column having aplurality of chambers disposed one above the other each adapted toreceive a liquid, means extending continuously through the chambers andadapted to convey the gaseous mixture in indirect contact with theliquids therein, means for supplying liquid produced by selectiveliquefaction of the gaseous mixture to one of the chambers, means forsupplying an extraneous liquid to another of the chambers, and means forwithdrawing vapor at a pressure below atmospheric from the chambercontaining the extraneous liquid.

22. An apparatus for separating a conadapted to receive a for supplyingliquidstituent which is not readily liquefiable from a gaseous mixture,comprising a column having a pluralit of chambers eachadapted to receivealiqui means extending through the chambers and adapted to convey, thegaseous mixture in indirect contact with the liquids therein, means forsupplying liquid produced by selective liquefaction of the gaseousmixture to one of the chambers, an means for supplying an extraneousliquid to another of the chambers, including means for liquefying agaseous medium by indirect contact with the liquid produced by selectiveliquefaction of the gaseous mixture and an auxiliary liquefaction cyclemaintained for the purpose of. supplying the gaseous medium.

23. An apparatus for separating a constituent which is not readilyliquefiable from a gaseous mixture, comprising a column having aplurality of chambers each adapted to receive a liquid, means extendingthrough the chambers and adapted to convey the gaseous mixture inindirect contact with the liquids therein, means for supplying liquidproduced by selective liquefaction of the gaseous mixture to one of thechambers, means for supplying an extraneous liquid toanother of thechambers, including means for liquefying a gaseous medium by indirectcontact with the liquid produced by selective liquefaction of thegaseous mixture and an auxiliary liquefaction cycle maintained for thepurpose of supplying the gaseous medium, and means for expanding theproducts .of the auxiliary cycle and to utilize the refrigerating effectthus developed.

24. An apparatus for separating a constituent w ich is not readilyliquefiable from a ga eous mixture, comprising a column havingaplurality of chambers each adapted to receive a liquid, means extendingthrough the chambers and adapted to convey the gaseous mixture inindirect contact with the liquids therein, means for supplying liquidproduced by selective liquefaction of the gaseous mixture to one of thechambers, means. for supplying an extraneous liquid to another of thechambers, including means for liquefying a gaseous medium by indirectcontact with-the liquid produced by selective liquefaction of thegaseous mixture and an auxiliary liquefaction cycle maintained for thepurpose of supplying the gaseous medium, and means for returning thegaseous medium to the auxiliary cycle for recirculation therein.

In testimony whereof I affix my signature.

CLAUDE C. VAN NUYS.

